There have been numerous cases of unintended acceleration of motor vehicles, resulting in property damages, injuries, even deaths and subsequent liability suits. The incidents have been reported in a variety of makes and models of motor vehicles. In the past few years, the passenger motor vehicles manufactured by Audi of West Germany have became notorious for many incidents of such unintended acceleration. The National Highway Traffic Safety Administration indicates that as many as 1,788 accidents have occurred with the Audi 5000 due to alleged unintended acceleration.
In most of the reported cases of unintended acceleration, the vehicle accelerated at or near full-throttle regardless of alleged efforts of the drivers to bring the vehicles to a stop, while the brakes seemed to be ineffective. The vehicle manufacturers blamed the driver's error, i.e., depressing the accelerator pedal rather than the brakes, however, the drivers and the consumer groups put the blame on mechanical faults of the vehicles. Mechanically, for this to happen, two failures must happen simultaneously; the engine stuck at full or near throttle, and brake failure. Automobile experts maintain that no engine in passenger motor vehicles is powerful enough to overcome normally functioning brakes to keep the vehicle accelerating under full brakes. Technologically, it seems to be very improbable for both failures to occur simultaneously. The more plausible cause for the unintended acceleration is the driver's error, as the vehicle manufacturers claim. It is possible, under certain circumstances, for a vehicle's driver to mistake the accelerator pedal for the brake pedal. Most people have such an experience, although they realize the mistake quickly and apply the brakes. However, when the driver does not realize the mistake and keeps depressing the accelerator as if it were the brake, the vehicle accelerates uncontrollably, and eventually accidents may occur. Recent tests by the automobile magazine Road & Track support this explanation. The U.S. Supreme Court also ruled in favor of Audi in recent liability suits against Audi involving unintended acceleration in Audi 5000's, determining drivers' pedal misapplication as the cause of unintended acceleration. Although it is not very clear whether pedal misapplication is the only cause of unintended acceleration, it is a much more likely cause than the simultaneous faults of the engine and brakes. The more frequent occurrence in certain makes and models of vehicles may be related to design aspects specific to such vehicles that may induce pedal misapplication.
A number of late-model passenger vehicles are equiped with an interlock mechanism frequently referred to as "shift lock". This mechanism is devised to prevent shifting into any other gear positions from "park" unless the brake pedal is depressed. This mechanism is claimed to be effective in reducing the incidents of pedal misapplication from a vehicle moving out of a parked position. However, this mechanism is not effective at all when pedal misapplication occurs in a moving vehicle. Some reports have claimed that the rate of unintended acceleration incidents in Audi 5000's did not go down significantly after all the cars were recalled to install the shift lock mechanism. Therefore, the effectiveness of the shift lock against unintended acceleration is not clear, or marginal best.
The present invention aims at more effective means of controlling unintended acceleration due to pedal misapplication. During normal driving, a driver modulates the pressure on the accelerator pedal to control the engine speed. In most passenger vehicles, only relatively light pressure on the accelerator is needed to open the throttle fully. However, when the driver mistakes the accelerator pedal for the brake, causing unintended acceleration, he depresses the accelerator pedal as hard as possible in a desperate attempt to bring the vehicle to a stop. In normally equiped vehicles, it causes the vehicle only to accelerate at a maxiumum rate, eventually causing an accident. The important observation to be made is that during the unintended acceleration, the driver depresses the accelerator pedal much harder than under normal driving conditions, because he thinks it is the brake. In the present invention, such an excessive pressure on the accelerator pedal is exploited to reduce the engine speed and/or to apply the brakes, so that the accelerator pedal acts as a brake when the driver mistakes it for the brake.